*** If unresolved symbols were reported above, they might not
*** be the reason for the server aborting.

Fatal server error:
Caught signal 11. Server aborting

There is no problem with my kernel headers. They match the running kernel
exactly (I compile the kernel myself). But in this case the unresolved symbols
do not refer to the compiled nvidia.ko module; they refer to the nvidia_drv.o
X driver that is supplied by Nvidia.